Midi-chlorians were intelligent microscopic life-forms that served as organelles within all living cells, existing in a symbiotic relationship with the beings they inhabited and comprising a collective consciousness amongst themselves.
I've seen this referenced elsewhere, but don't know where it came from in Star Wars canon. It seems to be quite important that midi-chlorians are intelligent, but there's nothing in the article or elsewhere that I've read or seen that shows there's any kind of intelligent behavior from midi-chlorians.
Is this just something that's been stated and not used, or are there instances in stories showing intelligent behavior or even something as exotic as communication between "regular" characters and midi-chlorians? If they're intelligent, couldn't they tell why someone was using the Force and refuse to act if it was something they didn't want to do?